Fuel formed of cellulosic and biosolid materials

ABSTRACT

A fuel preferably pelletized and method of forming a fuel including a quantity of a natural particulate cellulosic material and a quantity of a particulate biosolid material from a bioslurry effluent derived substantially from fats, oils and grease (FOG) found in non-edible food residuals from sanitary sewer drainage (SSD). The biosolid material and the cellulosic material are substantially homogenous, preferably having a moisture content of from about 5% to about 15% by weight and at least substantially minus 5 mesh. A quantity of particulate synthetic polymeric thermoplastic fines material may be added for increased fuel energy content.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not applicable

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

Not applicable

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to the field of solid fuels, and moreparticularly to a cellulosic based preferably pelletized fuel andmanufacturing process therefor utilizing a biosolid formed frombioslurry effluent derived from non-edible food residuals of fats, oilsand grease (FOG) collected in sanitary sewer drainage (SSD).

2. Description of Related Art

Due to diminishing quantities of coal, petroleum, and natural gasproducts, attention is being directed to other energy sources, includingoil shale, solar energy, and nuclear energy. One source which isreceiving considerable attention is biomass materials such as wood andits byproducts. This is somewhat ironic since the original source forenergy in the United States and the rest of the world was wood. In fact,U.S. Pat. No. 43,112 issued on Jun. 14, 1864 was directed to combiningsawdust, tar, wood cuttings or chippings, water, and coal-tar to form anartificial fuel.

Much attention has previously been directed to preparing briquettes fromwood waste. For example, L. H. Reineke wrote a U.S. Forest Research Noteentitled “Briquettes from Wood Residue”, in November, 1964 describingvarious techniques available for briquetting wood residue. In addition,U.S. Pat. Nos. 3,227,530, 3,635,684, 3,843,336, 4,015,951 and 4,043,764describe techniques for briquetting cellulosic material.

Use of available pelletized wood waste as a fuel source has achievedonly limited acceptance to date. One reason for this is the relativelylow heating value of pelletized wood as compared to coal. Pelletizedwood can have a heating value of less than 7,000 BTU's per pound, whilecoal generally has heating value in excess of 9,000 BTU's per pound.Therefore, the transportation and handling costs associated withavailable pelletized wood are higher per BTU than for coal.

Other problems with use of available pelletized wood as a fuel sourceare that it has a slow burning rate and it exhibits incomplete burnout,resulting in formation of carbonaceous residues and low combustionefficiency. In addition, pelletized wood can be harder to ignite thancoal and pelletized wood can be more fragile than coal, requiringspecial handling to avoid crumbling and to prevent weathering. Toovercome the crumbling and weathering problems, inorganic binders suchas cement and silicate of soda, and organic binders such as tar, pitch,rosin, glues, and fibers have been included in the pellets. However, nobinder has been found which solves the above problems, and which also isinexpensive and does not reduce the heating value of the wood.

It has been attempted to use the self-binding characteristics of variousspecies of wood due to lignin present to avoid the crumbling problem.This can be affected with some species of wood, but not all species, byheating the wood above its minimum plastic temperature of 325.degree. F.as reported by Reineke in the above-mentioned U.S. Forest ServiceResearch Note, and also as reported by Gunnerman in the above-mentionedU.S. Pat. No. 4,015,951. However, such high temperatures can severelylimit the operating life of the pelletizing equipment and drive high BTUvolatile components from the wood.

Therefore, there was a need for a fuel pellet which resists crumbling,is easily ignitable, burns fast and completely, and has a heating valueapproaching that of coal; and there is also a need for a method forpreparing the fuel pellet which does not require high pelletizingtemperature.

In U.S. Pat. No. 4,529,407 (incorporated herein by reference), Iinvented a fuel pellet with the above features and a method forpreparing the fuel pellet. The fuel pellet, which preferably has aminimum dimension of at least 3/16 inch for ease of handling, comprisesfrom about 50 to about 99% by weight natural cellulosic material, andfrom about 1 to about 50% by weight synthetic polymeric thermoplasticmaterial. The thermoplastic material was chosen so it is solid at roomtemperature and has an injection molding temperature of at least200.degree. F. The thermoplastic material serves to bind the pellettogether, increases the heating value of the pellet, lubricates thepelletizing die, and improves the ignition and burning characteristicsof the pellet. Fuel pellets of the '407 patent exhibit complete burnout,burn faster than pellets not containing thermoplastic material, and canhave a heating value in excess of 9,000 BTU's per pound. Preferably, thethermoplastic material is uniformly distributed throughout the fuelpellet.

The '407 fuel pellet was made by preparing a feed comprising from about50% to about 99% of particulate natural cellulosic material and fromabout 1% to about 50% by weight of particulate synthetic thermoplasticmaterial. The cellulosic material has a free moisture content of fromabout 5 to about 15% by weight, and preferably substantially all of thecellulosic material was −5 mesh. Substantially all of the thermoplasticmaterial was −5 mesh, and preferably −10 mesh. The plastic andcellulosic materials are intimately combined by compressing the feed ina die.

The foregoing examples of the related art and limitations relatedtherewith are intended to be illustrative and not exclusive. Otherlimitations of the related art will become apparent to those skilled inthe art upon a reading of the specification and a study of the drawings.

The following embodiments and aspects thereof are described andillustrated in conjunction with systems, tools and methods which aremeant to be exemplary and illustrative and not limiting in scope. Invarious embodiments one or more of the above-described problems havebeen reduced or eliminated while other embodiments are directed to otherimprovements. In addition to the exemplary aspects and embodimentsdescribed above, further aspects and embodiments will become apparent byreference to the drawings and by study of the following descriptions.

BRIEF SUMMARY OF THE INVENTION

This invention is directed to A fuel pellet and method of forming a fuelpellet including a quantity of a natural particulate cellulosic materialand a quantity of a particulate biosolid material from a dried bioslurryeffluent derived substantially from fats, oils and grease (FOG) found innon-edible food residuals from sanitary sewer drainage (SSD) interceptortanks. The biosolid material and the cellulosic material aresubstantially homogenous and solid at room temperature, preferablyhaving a moisture content of from about 5% to about 15% by weight and atleast substantially minus 5 mesh. A quantity of particulate syntheticpolymeric thermoplastic fines material may be added for increased fuelcontent.

It is therefore an object of this invention to provide pellet fuelutilizing previously combustible cellulosic matter combined withbiosolid material derived from non-combustible grease interceptorssolids of fat, oils, and grease (FOG).

It is yet another object of this invention to provide an alternate meansfor disposing of the bioslurry of FOG and biomass non-edible foodresiduals in sanitary sewer drainage inclusive of “gray water” collectedas a disposable byproduct from food preparation facilities.

Still another object of this invention is to build on the technology ofmy prior U.S. Pat. No. 4,529,407 and the fuel pelletizing technologydisclosed therein in formulating a new fuel pellet which combines withthe FOG and other non-edible greasy food residuals collected fromsanitary sewer drainages associated with food preparation facilitiessuch as restaurants.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 illustrates in a perspective view a pellet representative ofpellets prepared according to the teachings of U.S. Pat. No. 4,529,407;

FIGS. 2A and 2B illustrate the process of the '407 patent and are to beconsidered serially.

FIG. 3 is a flow diagram of the process of manufacturing the new fuelpellet formulation of the present disclosure.

Exemplary embodiments are illustrated in reference figures of thedrawings. It is intended that the embodiments and figures disclosedherein are to be considered to be illustrative rather than limiting.

DETAILED DESCRIPTION OF THE INVENTION Prior Art

(A portion of the Detailed Description in U.S. Pat. No. 4,529,407 isreproduced hereinbelow).

With reference to FIG. 1, there is shown a fuel pellet 10 prepared fromcellulosic material and thermoplastic material. Fuel pellet 10, which iscylindrical in shape, has a minimum dimension of at least 3/16 inch andcomprises from about 50 to about 99% by weight natural cellulosicmaterial and from about 1 to about 50% by weight thermoplastic material.As is more fully set forth below, these fuel pellets are easilyignitable, burn evenly, quickly and completely, resist weathering, andgenerally have a gross heating value in excess of 9,000 BTU's per pound,and can have a gross heating value in excess of 10,000 BTU's per pound.

The natural cellulosic material used to form the pellets 10 can beparticulate woody material such as sawdust, wood shavings, sander'sdust, hog fuel, peat, and bark. Agricultural waste such as banana andpapaya stalks, straw, bamboo, jute, bagasse, corn husks, corn cobs,cotton “gin trash”, sisal, seed hulls, and peanut hulls can also beused. Also, paper and cardboard can be included in the pellets.Combinations of the above natural cellulosic materials can also be used.Preferred natural cellulosic materials are these with low moisturecontent to minimize drying costs and low contamination levels tominimize pelletizer die wear. As used herein, the term “cellulosicmaterial” includes lignin. Particulate woody material preferably is usedin the pellets because it has a higher heating value and lower moisturecontent than agricultural waste.

Inclusion of banana and/or papaya stalks in the pellets is desirablebecause banana and papaya latex are good binding agents and contributeto the cohesiveness of the pellets. The synthetic thermoplastic materialcan be practically any available synthetic thermoplastic such as, butnot limited to, polystyrene, polyethylene, polypropylene,acrylonitrile-butadienestyrene, acetyl copolymer, acetyl homopolymer,acrylic, polybutylene, and combinations thereof. Although thermoplasticscontaining a halogen such as polyvinylchloride can be used, for mostapplications there are to be avoided, because of corrosion and emissionproblems associated with the combustion products of halogen-containingthermoplastics. It has been noted that for fast burning and ease ofignition of the fuel pellets, polypropylene and polyethylene are thepreferred synthetic thermoplastic materials.

The term “synthetic thermoplastic materials” excludes naturallyoccurring thermoplastic materials and naturally occurring cellulosicmaterials. For ease of handling, the synthetic thermoplastic materialmust be solid at room temperature. Preferably the syntheticthermoplastic material has an injection molding temperature of at least200° F.

It is critical to the ('407) invention that at least 1% by weightthermoplastic material be included in the fuel pellets. This is becausefuel pellets containing thermoplastic material have many significantadvantages compared to fuel pellets containing only cellulosic material.For example, inclusion of thermoplastic material in fuel pellets allowsthe fuel pellets to be formed easily in a pelletizer at temperatureslower than temperatures required for forming a fuel pellet with onlycellulosic material. Thus, the thermoplastic material serves as aprocessing aid for forming pellets from the cellulosic material. Inaddition, the thermoplastic material has a higher heating value than thecellulosic material, and the resulting pellets have a correspondinglyhigh heating value.

Another advantage of the presence of synthetic thermoplastic material infuel pellets is that the thermoplastic material provides a substantiallywater-impervious coating, or sheath on the outside of the pellets,thereby both preventing uptake of moisture by the pellets and resistingweathering in storage. Because of the uniform distribution of theplastic in the pellets, there is plastic even at the ends of acylindrical pellet. This also prevents uptake of water by the pellets.Furthermore, the hydrophobic nature of the plastic prevents wateruptake. Pellets of the present invention have been left out overnight inthe rain and still maintained their cohesiveness, while conventionalwood pellets tend to disintegrate when wet. A portion of thethermoplastic material can be in the fuel pellets in the form ofdiscrete subparticles, although it is preferred that the thermoplasticmaterial be substantially uniformly distributed throughout theparticles. The presence of discrete thermoplastic subparticles in fuelpellets results in easy ignition because the discrete subparticlesprovide an ignition situs.

Exemplary of such (cellulosic) materials which can be included arecoconut husks, soy beans, peanuts, sunflower seeds, corn cake, pressingresiduals, and the like.

As used herein, the term “pellet” refers to a discrete particle of anysize or shape which contains both natural cellulosic material andsynthetic thermoplastic material. The pellet need not be symmetrical,but it is preferred that the pellet 10 be substantially symmetrical inshape such as cylindrical, parallel-piped or the like, having a diameterwithin the range of from about 3/16 inch to about 1 inch. While it ismost practical to form the pellets in a cylindrical shape, the pelletscan be in any suitable symmetrical configuration such as the shape of acube. Pellets have been produced which are cylindrical in shape, such asthe pellet shown in FIG. 1, having a length of about 1 inch and adiameter of about ⅜ inch. For such a pellet, the “minimum dimension” ofthe pellet is the diameter, i.e. ⅜ inch.

A process for preparing fuel pellets is shown schematically in FIGS. 2Aand 2B. Cellulosic feed material, plastic feed particles, and plasticfeed sheet are delivered by trucks (not shown) and stored in storagebins 20 a, 20 b, and 20 c, respectively. Additional feed storage binscan be provided for segregating different types of feed. The feed,either before or after introduction into the feed bins, can be treatedto separate foreign materials such as metallic impurities and soil. Thiscan be done by means of such equipment as pneumatic conveyors, screens,magnets, and combinations thereof. Magnets conventionally are built intothe equipment, described below, used for comminuting the feed materials.The feed from the cellulosic feed storage bin 20 a is transferred via abelt conveyor 24 a to a classifying device such as a vibrating screen 26to separate oversize particles 28 from particles 30 which are suitablefor direct feed to a pelletizing operation. The size of the holes in thescreen depend upon the size of the pellets to be made, but in any case,the size of the holes is necessarily smaller than the minimum dimensionof the pellets. For example, if cylindrical pellets having a diameter of3/16 inch are to be made, then the size of the holes in the screen isnecessarily less than 3/16 of an inch. In the version of the processshown in FIG. 1, the screen segregates particles greater than ⅛ inch indiameter, and passes these particles to a comminution device such as ahammer mill 32.

The particles 30 not requiring comminution and the comminuted particles34 from the hammer mill 32 are collected on a belt conveyor 36 andpassed via ducts 37 to two rotary dryers 38 in parallel to reduce themoisture content of the cellulosic material. To develop the necessarystrength and hardness in the pellets, it is essential that the freemoisture content of the cellulosic material be reduced to less thanabout 15% by weight. By “free moisture” there is meant moisture whichcan be removed by evaporation at normal temperatures and does notinclude any bound water such as chemically bound water that might bepresent in the feed material. Various types of dryers such assteam-heater plates, and dry steam pipes over which the feed is cascadedcan be used to bring the feed to the desired moisture content. Flashdryers using a short exposure to hot gases can be used. The heat fromdrying can be provided by burning the fuel pellets and/or fines producedby this process in a heater 40 (suspension-arc burner in FIG. 3) whichsupplies hot gas via ducts 41 to the dryers.

Water can be removed from the feed material upstream of the dryers whenthe feed material contains gross quantities of water For example, watercan be removed from peat, bark, or sawdust with presses that operate onthe roller or clothes-wringer principle. Screw presses, using taperedscrews, are also useful for dewatering of bark. The drying operation canbe run as a batch operation to avoid the expense of duplicating drying,cooling and conveying equipment for different cellulosic feed materials.The gases and water evolved in the dryers 38 are withdrawn from thedryers via lines 42 into two cyclones 44 in parallel, one for eachdryer, by an exhaust fan 46. The discharge from the fan 46 can be passedto a dust collector (not shown) or passed directly to the atmosphere.Particulate matter withdrawn via line 42 is separated in the cyclones 44and dropped into a fines bin 47. The particulate matter in bin 47 is fedby a rotary valve 48 to a fines bin 77 (FIG. 2A). The dried feedmaterial is transferred by a storage bin tank feed conveyor 49 to one ormore storage bins 52 a or 52 b (FIG. 2B). The different storage bins areused for storing different types of feed material. More storage binsthan the two storage bins shown in FIG. 2A can be used. The storage bins52 a and 52 b preferably are tumble bins to avoid compaction of the feedmaterial and to maintain dehydration of the feed. A rotary cooler (notshown) using ambient air to cool the material discharged by the dryercan be used if required, to avoid caking of the feed material instorage.

The plastic feed is passed from the plastic feed bins 20 b and 20 c viabelt conveyor 24 b and 24 c, respectively, to comminution devices suchas granulators 56 a and 56 b, respectively. The smaller the particlesize of the thermoplastic feed, the stronger the fuel pellets and themore even and uniform their burning characteristics, and the lessplastic required in the fuel pellets. In addition, when the pellets areto be pulverized before burning, it is important that the plastic becomminuted to a small size so that each particle resulting from thepulverization contains both plastic and cellulosic material. Therefore,the granulators are operated so that substantially all of theparticulate thermoplastic material is minus 5 mesh. Preferably, thebulk, i.e., at least 50% by weight of the particulate thermoplasticmaterial is −10 mesh, and more preferably substantially all is minus 10mesh. It is believed that optimumly substantially all of the plastic is−20 mesh. The comminuted plastic feed discharged by the granulators 56 aand 56 b passes to belts 57 a and 57 b, respectively, for transport toplastic feed storage bins 52 c and 52 d, respectively. More than twoplastic storage bins can be used if required.

Each of the storage bins has associated with it a weigh belt conveyor 62a, 62 b, 62 c, or 62 d. The four conveyors 62 a, 62 b, 62 c, and 62 dare used to provide the proper weight ratios of the feed materials to apellet mill 70. The four conveyors drop their feed onto a belt conveyor64 which carries it to a chamber 65 for preheating of the feed with drysteam, if desired. From the chamber 65 the feed passes into a mixer 66such as a combination mill to obtain uniform mixing of the differenttypes of feed material. The mixer discharges mixed feed onto a beltconveyor 67 which lifts the feed to a pellet mill feed bin 68. The feedis gravity fed from the bin 68 to a conveyor 69 which drops the feedinto the pellet mill 70 in which the pellets of the present invention,such as a pellet shown in FIG. 1, are formed. Any suitable pelletizingmachine can be used such as, for example, the one produced by theCalifornia Pellet Mill Company of San Francisco, Calif. or the millproduced by Koppers Sprout-Walden Company. In this apparatus, thematerial is fed into a hopper and pressed into dies having the desiredconfiguration and shape.

The pellet mill must be capable of producing a pressure in the dieduring compression which causes the temperature of the feed material toincrease so that the pellets have a temperature of from about 150° toabout 250° F. where they are discharged from the pellet mill, i.e. wherethe pressure is released. When the discharged pellets are at atemperature in excess of about 250° F., degradation and carbonization ofthe thermoplastic material can occur, and when the discharged pelletsare at a temperature of less than about 150° F., the pellets can haveinsufficient cohesiveness. Preferably, the discharge temperature of thepellets is from about 190° to about 210° F. to produce pellets withexcellent burning properties and good cohesion. As the dischargetemperature of the pellets increases, their density increases. Forexample, pellets containing 5% by weight polyethylene and 95% by weightsawdust had a density of 31 pounds per cubic foot when discharged from apelletizer at 190° F., and a density of 34 pounds per cubic foot whendischarged from the pelletizer at a temperature of 199° F. Supplementalheat and moisture for the pellet mill 70 can be provided by steam 71which can be generated in a boiler 72 fueled by pellets produced by thisprocess or reject fines. The steam can be used for drying the feed inthe dryers 38.

From the pellet mill, the formed pellets are cooled in a cooler 72 byambient air supplied by a blower 73, and transferred to a screen 74 forseparation of any fines 75 which are carried by a conveyor 76 to a finesstorage bin 77. The fines are transferred from the storage bin 77 by arotary valve 78 and a blower 79 for feed to the boiler 72 used togenerate steam for the pellet mill. The product pellets 80 can be sentto storage, bagged, or transferred to trucks or railroad cars forshipment.

The Present Invention

Building upon the teaching of my '407 patent, and generally utilizingthe manufacturing process previously described, a use for a previouslydiscarded food preparation facility byproducts in the form ofnon-combustible combinations of grease interceptors solids of fat, oilsand grease (FOG) and non-edible food residuals in sanitary sewerdrainage (SSD, known as “gray water”) is now incorporated into the fuelpellet of the present invention. These non-combustible previouslydiscarded food preparation facility byproducts are now being collectedin subsystems of restaurants designed for this purpose. The collectedbyproducts are then drained into storage interceptor tanks for timelypick up and removal by mobile tankers to a pretreatment facility whereoverflow gray water is recycled to EPA standards.

Until now, the reuse opportunities for this otherwise non-combustiblebioslurry which is collected by grease removal devices (GRD) interceptorwater systems have overlooked the fact that the FOG is a carbon richeffluent resource when properly dewatered and treated when combinedparticulate cellulose under the teachings of this disclosure. Inaddition to obtaining the resultant FOG which has a commerciallyacceptable level of BTU energy, particularly when supplemented byparticulate plastic fines, this invention has many additional sidebenefits related to avoiding landfill disposal thereof, self adhesivepellet binding, lubrication and extended life of pellet mill dies usedto extrude the finished product, and the resultant higher manufacturingcapacity and improved economics provided thereby.

Referring now to FIG. 3, a multi-facet process plant is there shown inflow diagram format at numeral 100. The origin of the bioslurry beginsin the food preparation kitchen at 102 wherein a wash up macerator 104deposits the effluent discharge at 106 into interceptor tank grease pittrap system at 108. The gray water overflow at 110 is then distributedto a sanitary drainage system at 112. From there, the bioslurry may beeither disposed of into a sewer at 112 or recycled at 114.

In the present invention 100, the fats, oils and grease (FOG) in thebioslurry are pumped at 116 into a mobile tanker 120 or, alternatively,into a condenser settlement tank 118 for water/solids separation fordisposal at 122 or transported into a receiving tanker discharge at 124ready for pretreatment operations at 130.

Pretreatment operations at 130 include a mixer/macerator blender 132which receives the partially dewatered FOG biosolids from 124 alsoreceived into the blender 132 is cellulosic particulate from silo 134which has been processed as previously described in FIGS. 2A and 2Bpreviously described and received from conveyor 49 also shown in FIG.2B. This blending of the raw material from 124 and the preparedcellulosic particulate from silo 134 within the blender 132 also servesto additionally dewater the fuel being prepared within the blender 132down to about 50% moisture by weight or greater for further processing.

This blended mixture of cellulosic particulate and partially processedFOG is then fed into a screw press 136 or alternately into a rotarysieve dewatering drum and knife scraper 138 for further dewatering.Thereafter, the dewatered and concentrated slurry cake ofnear-combustible material is then discharged in the form of a biocake ofsemi-dry solids at 140. This biocake material having a moisture contentin the range of about 25% by weight is then fed into a rotary drum dryer144 which further dries the fuel mixture down to a moisture content inthe range of up to 15%. Once dried, the fuel material is then shipped at142 in particlized form ready for use as a fuel or fed into asieve/screen/pulverize stage at 146 which properly adjusts the overallsize of the material to specification, preferably the size of aboutminus 5 mesh size and no greater for the purpose of pelletizing. Notealso that the fuel being shipped at 152 has a maximum particle size ofabout minus 5 mesh to be used in a suspension arc burner.

The properly pulverized, sized and dried fuel material is then fed intoa densification press or pelletizer 150 or alternately to a storage silo148 for conveyance into the pelletizer 150 at a later time. Thepelletized fuel is then fed into a rotary cooler 154 using ambient airto cool the pelletized fuel, then into a storage silo 156 ready forshipment at 158.

To enhance the energy content of the pelletized fuel, particulateplastic fines at 160 may be introduced into the pulverizing stage at146. As previously described, the BTU content may increase to an averageup to 14,000 BTUs from the original maximum of 7,000 BTUs of thecellulosic material. Particulate biomass material at 162 may also beintroduced into the pulverizing stage at 146 to help further dry and addto the energy content of the pelletized fuel. This biomass material at162 may include sawdust, bark, wood shavings, sand or dust, hog fuel,peat and agricultural waste such as stalks, straw, bamboo, jute,bagasse, corn husks, cob cotton, gin trash, sisal, seed hulls and peanuthulls as well as paper, and cardboard, all having been previouslyparticlized to size of an overall negative 5 mesh maximum.

To provide additional energy for the rotary drum drier 144, the finesrecycle energy step at 164 gathered from the pulverizing stage 146 maybe recycled into the suspension burner 166 which delivers this dryingheat into the rotary drum drier 144 for additional drying efficiency ofthe fuel particulate.

To repeat, while pelletizing of this new fuel source is preferred, otherforms of the prepared particulate cellulosic/biosolid fuel areenvisioned within the scope of this invention.

While a number of exemplary aspects and embodiments have been discussedabove, those of skill in the art will recognize certain modifications,permeations and additions and subcombinations thereof. It is thereforeintended that the following appended claims and claims hereinafterintroduced are interpreted to include all such modifications,permeations, additions and subcombinations that are within their truespirit and scope.

1. A fuel pellet consisting essentially of a homogeneous mixture of: aquantity of natural particulate cellulosic material; and a quantity ofbiosolid material made from a dried bioslurry effluent derived fromfats, oils and grease (FOG) found in non-edible food residuals fromsanitary sewer drainage (SSD).
 2. The fuel pellet as set forth in claim1, wherein: said quantity of cellulosic material is about 80% by weightof said fuel; and said quantity of biosolid material is about 20% byweight of said fuel.
 3. A method for preparing a fuel pellet fromparticulate natural cellulosic material and biosolid material consistingof: providing particulate natural cellulosic material having a moisturecontent of at least about 5% by weight; providing biosolid materialconsisting essentially of fats, oils and grease (FOG) derived fromnon-edible food residuals from santitary sewer drainage (SSD); preparinga homogenous mixture including said particulate cellulosic material andsaid biosolid material; and pelletizing said mixture by compressing andextruding said mixture.
 4. A fuel pellet consisting essentially of ahomogeneous mixture of: a quantity of natural particulate cellulosicmaterial; a quantity of biosolid material from a dried bioslurryeffluent derived from fats, oils and grease (FOG) found in non-ediblefood residuals from sanity sewer drainage (SSD); and a quantity ofparticulate synthetic polymeric thermoplastic material;
 5. The fuelpellet as set forth in claim 4, wherein: said quantity of cellulosicmaterial is about 78% by weight of said fuel pellet; said quantity ofbiosolid material is about 18% by weight of said fuel pellet; saidquantity of thermoplastic material is about 2% by weight of said fuelpellet.
 6. A method of preparing a fuel from particulate naturalcellulosic material, biosolid material, and particulate syntheticpolymeric thermoplastic material consisting of: providing naturalparticulate cellulosic material having a free moisture content of atleast about 5% by weight; providing biosolid material consistingessentially of fats, oils and grease (FOG) derived from non-edible foodresiduals from sanitary sewer drainage (SSD); providing particulatesynthetic polymeric thermoplastic material; and preparing a homogenousfuel mixture including said cellulosic material, said biosolid material,and said thermoplastic material.
 7. The method of claim 6, furthercomprising the step of: sieving said mixture to a maximum of minus 5mesh.
 8. The method of claim 7, further comprising the step of:compressing and extruding the fuel in a die at a pressure wherein thetemperature of the resulting said fuel pellets emerging from the die arefrom about 60° C. to about 125° C., and substantially remainingparticulate. 9-12. (canceled)